The elastic scattering of 6He on 208Pb has been measured at laboratory energies of 14, 16, 18 and 22 MeV. These data were analyzed using phenomenological Woods–Saxon form factors and optical model calculations. A semiclassical polarization potential was used to study the effect of the Coulomb dipole polarizability. Evidence for long range absorption, partially arising from Coulomb dipole polarizability, is reported. The energy variation of the optical potential was found to be consistent with the dispersion relations which connect the real and imaginary parts of the potential.status: publishe

The first measurement of the elastic scattering of the halo nucleus ${}^{11}\mathrm{Li}$ and its core ${}^9\mathrm{Li}$ on ${}^{208}\mathrm{Pb}$ at energies near the Coulomb barrier is presented. The ${}^{11}\mathrm{Li}+{}^{208}\mathrm{Pb}$ elastic scattering shows a strong reduction with respect to the Rutherford cross section, even at energies well below the barrier and down to very small scattering angles. This drastic change of the elastic differential cross section observed in ${}^{11}\mathrm{Li}+{}^{208}\mathrm{Pb}$ is the consequence of the halo structure of ${}^{11}\mathrm{Li}$, as it is not observed in the elastic scattering of its core ${}^9\mathrm{Li}$ at the same energies. Four-body continuum-discretized coupled-channels calculations, based on a three-body model of the ${}^{11}\mathrm{Li}$ projectile, are found to explain the measured angular distributions and confirm that the observed reduction is mainly due to the strong Coulomb coupling to the dipole states in the low-lying continuum of ${}^{11}\mathrm{Li}$. These calculations suggest the presence of a low-lying dipole resonance in ${}^{11}\mathrm{Li}$ close to the breakup threshold.

Experimental results of the elastic scattering of 6He on 208Pb at ELAB=22 MeV, measured at the CRC facility (Louvain-la-Neuve, Belgium), are presented, including results on the 4He production channel. These data were taken with full angular coverage and high angular resolution. Both experimental cross sections are compared with continuum discretized coupled channels and distorted-wave Born approximation calculations, where direct breakup and transfer to the continuum processes are considered. The elastic data confirm the absence of the Coulomb rainbow, while the distribution of $\alpha${} particles indicates that such production is mostly generated by transfer to the continuum.

The inclusive breakup for the ${}^{11}\mathrm{Li}+{}^{208}\mathrm{Pb}$ reaction at energies around the Coulomb barrier has been measured for the first time. A sizable yield of ${}^9\mathrm{Li}$ following the ${}^{11}\mathrm{Li}$ dissociation has been observed, even at energies well below the Coulomb barrier. Using the first-order semiclassical perturbation theory of Coulomb excitation it is shown that the breakup probability data measured at small angles can be used to extract effective breakup energy as well as the slope of $B(E1)$ distribution close to the threshold. Four-body continuum-discretized coupled-channels calculations, including both nuclear and Coulomb couplings between the target and projectile to all orders, reproduce the measured inclusive breakup cross sections and support the presence of a dipole resonance in the ${}^{11}\mathrm{Li}$ continuum at low excitation energy.

Angular distributions of the elastic, inelastic, and breakup cross sections of the halo nucleus ${}^{11}\mathrm{Be}$ on ${}^{197}\mathrm{Au}$ were measured at energies below ($E_{\text{lab}}=31.9\mathrm{MeV}$) and around (39.6 MeV) the Coulomb barrier. These three channels were unambiguously separated for the first time for reactions of ${}^{11}\mathrm{Be}$ on a high-$Z$ target at low energies. The experiment was performed at TRIUMF (Vancouver, Canada). The differential cross sections were compared with three different calculations: semiclassical, inert-core continuum-coupled-channels and continuum-coupled-channels ones with including core deformation. These results show conclusively that the elastic and inelastic differential cross sections can only be accounted for if core-excited admixtures are taken into account. The cross sections for these channels strongly depend on the $\mathcal{B}(E1)$ distribution in ${}^{11}\mathrm{Be}$, and the reaction mechanism is sensitive to the entanglement of core and halo degrees of freedom in ${}^{11}\mathrm{Be}$.